Mutation to DNA is a primary mechanism by which cancers arise. These events have also been implicated in diseases such as atherosclerosis, and processes such as aging. Therefore, there is an important need for sensitive analytical methods that facilitate the study of mutagenesis, as well as the identification of chemical or physical agents that can mutate DNA. Methods for measuring in vivo mutation currently exist, each with their own advantages and limitations. While some are based on colony formation and require tissue culture work, others rely on expensive, proprietary trangenic rodents. This laboratory has developed an in vivo mutation assay that is based on the Pig-a locus. The Pig-a gene product is essential for the biosynthesis of glycosyl phosphatidylinositol (GPI) anchors. Mutations giving rise to nonfunctional GPI anchors prevent certain proteins from being expressed on the cell surface, and this represents a phenotype that can be measured by flow cytometry. The work proposed herein extends this line of investigation through an extensive inter-laboratory validation effort whereby rats will be treated with known mutagens and non-mutagens using both a short-term as well as a 28-day repeat dosing schedule. This assay validation effort will focus on an erythrocyte-based assay, a target cell population that has been studied most intensely to date. Concurrently, other work will be directed at developing means to measure Pig-a mutation in other tissues. Society will benefit from the proposed work as pharmaceutical and chemical companies are provided improved methods for conducting safety assessment work. PUBLIC HEALTH RELEVANCE: It is well known that DNA damage is a precursor to the development of cancer and other significant diseases. Therefore, it is in the interest of public health to reduce the occurrence of mutagenic chemicals in the environment, in our drugs, and from our workplaces. This research project will validate a powerful blood-based method that detects mutagenic agents, thereby enhancing the nation's ability to effectively reduce exposure to these toxic compounds. Additional work will be directed at developing mutant cell scoring methods that are compatible with other tissues.